The invention relates to a tire inflation pressure control system and method in motor vehicles.
Such a system is known, for example, from German Patent document DE 41 29 554 A1 or the present assignee's German Patent document DE 195 32 386 A1. Systems of this type, in particular, have sensor devices in the interior of the tire of each wheel. These sensor devices detect, for example, the air pressure and/or the temperature in the interior of the tire, convert these physical quantities to a corresponding voltage, and transmit this information to a stationary evaluation device arranged in the vehicle. This information transmission preferably takes place in a wireless manner by use of transponders.
If, for example, “tire inflation pressure” and “temperature” information is transmitted to the evaluation device, the evaluation device will compare the tire inflation pressure, for example, with a minimally permissible threshold value that is dependent on the temperature. If there is a falling below this minimally permissible threshold value, it can be indicated to the driver by way of the evaluation device which wheel has an insufficient tire inflation pressure. For this purpose, the evaluation device has to be informed at least once as to which sensor device is assigned to which wheel. In the system according to German Patent document DE 195 32 386 A1, such an assignment automatically takes place by way of a rotational-direction sensor in the wheels in connection with a driving direction determination.
In addition, from the assignee's European Patent document EP 1 293 362 B1, a process is known for determining the tire air pressure and a tire stress quantity in the form of a so-called wheel load, the wheel load being determined by way of the tire contact area measured by a deformation sensor.
It is an object of the invention to improve a device of the above-mentioned type such that, on the one hand, a timely warning is emitted, but premature warnings or erroneous warnings are avoided.
This and other objects are achieved according to the invention by providing a tire inflation pressure control system and method in a vehicle having at least a sensor for detecting the outside temperature and a sensor device on each wheel, which transmits at least the current tire inflation pressure and the current tire temperature of the respective wheel to an evaluation device fixedly arranged in the vehicle. During an initialization operation, the evaluation device stores at least the respective tire inflation pressure and the current outside temperature as initialization values, detects their current values during the drive and, within the scope of an air loss monitoring function as well as within the scope of a separate outside-temperature-dependent load capacity monitoring function, prompts the output of at least one early warning by way of an output unit.
The invention is based on the following considerations: in the case of current tire inflation pressure control systems, in principle, the following warning strategy is in the foreground.